No autopilot that I am aware of will keep the airplane in roll trim. The servos exert no force when they are off, so they can't correct an out of trim situation. When engaged, they can deal with a pretty out of trim plane, but when you disengage you now have to hand fly the untrimmed airplane.
There are some systems that can drive a PITCH trim servo and keep the airplane trimmed while the autopilot is engaged, but these need an electric trim servo and the assumption is always that you have buttons to manually adjust it while the AP is off. These buttons and drivers are built into the VP-X.